Polycarbonate resins are resins that exhibit an excellent heat resistance, excellent mechanical properties, and excellent electrical properties and are thus widely used as, for example, automotive materials, materials for electric and electronic equipment, housing materials, and materials for manufacturing parts in other industrial fields. In particular, flame-retarded polycarbonate resin compositions are advantageously used for parts in, for example, office automation equipment and information processing equipment, e.g., computers, notebook personal computers, cell phones, printers, copiers, and so forth.
The incorporation of a halogen flame retardant into polycarbonate resin has heretofore been used as a means for providing polycarbonate resins with flame retardancy. However, polycarbonate resin compositions that incorporate a halogen flame retardant containing chlorine or bromine exhibit a reduced thermal stability and cause corrosion of a screw and molding tools of molding equipments during the molding process. Numerous polycarbonate resin compositions that incorporate a phosphorus flame retardant are therefore in use as an alternative means here (refer, for example, to Patent Documents 1 and 2).
This incorporation of a phosphorus flame retardant in polycarbonate resins is an approach that can effectively shorten the burning time by, for example, film formation by the phosphorus compound at the resin surface or a dilution effect on the combustion gases in the gas phase by the phosphorus compound. However, a problem here is the substantial reduction in the impact resistance natively possessed by polycarbonate resins. Due to this, formulations that additionally incorporate an elastomer have been pursued. The present applicant has made various proposals, as in Patent Documents 3 to 7, with regard to such polycarbonate resin compositions that incorporate a phosphorus flame retardant and an elastomer.
Thus, Patent Document 3 provides a polycarbonate resin composition for which the generation of white foreign material spots on the molding surface is suppressed; this is achieved by the incorporation into an aromatic polycarbonate resin of a phosphorus flame retardant and a special anti-dripping agent in the form of an organic polymer-coated polyfluoroethylene. Patent Document 4 provides a polycarbonate resin composition in which the following are incorporated in an aromatic polycarbonate resin: a phosphorus flame retardant, a polyfluoroethylene, and a polyorganosiloxane-containing graft copolymer in which first and second vinyl monomers are copolymerized in prescribed proportions. Patent Document 5 provides a polycarbonate resin composition in which a phosphorus flame retardant, a vinyl monomer-grafted silicone/acrylic composite rubber, and an anti-dripping agent are incorporated in an aromatic polycarbonate resin in prescribed proportions.
Patent Document 6 provides a polycarbonate resin composition in which talc is essential and the following are incorporated in specific proportions in an aromatic polycarbonate resin: a phosphorus flame retardant, polyfluoroethylene, and a polyorganosiloxane-containing graft copolymer obtained by the copolymerization of a first vinyl monomer, a second vinyl monomer, and a multifunctional vinyl monomer in specific proportions in the presence of a specific amount of polyorganosiloxane particles. Patent Document 7 provides a polycarbonate resin composition in which the following are incorporated in specific proportions in a polycarbonate resin: a phosphorus flame retardant; a fluoropolymer; a polymer having a multilayer structure of a crosslinked polyalkyl acrylate core and an alkyl (meth)acrylate polymer-type shell; titanium oxide; carbon black; and a dye or pigment.
Patent Document 1: Japanese Patent Application Laid-open No. S59-202240
Patent Document 2: Japanese Patent Application Laid-open No. S62-4746
Patent Document 3: Japanese Patent Application Laid-open No. 2007-154173
Patent Document 4: Japanese Patent Application Laid-open No. 2008-280491
Patent Document 5: Japanese Patent Application Laid-open No. 2009-7487
Patent Document 6: Japanese Patent Application Laid-open No. 2008-285507
Patent Document 7: Japanese Patent Application Laid-open No. 2011-57888